The magnetic moment of $Gd^{3+}$ is ....... $B.M.$ $(Z = 64)$

Determine whether the following statements are True $(T)$ or False $(F)$:
$(a)$ The magnetic moment arises from the spin and orbital motion of electrons.
$(b)$ The magnetic moment of $Mn^{2+}$ is $5.92 \ BM$.
$(c)$ Interstitial compounds are covalent compounds.

The spin-only magnetic moment value of $M^{3+}$ ion (in gaseous state) from the pairs $Cr^{3+}/Cr^{2+}$,$Mn^{3+}/Mn^{2+}$,$Fe^{3+}/Fe^{2+}$,and $Co^{3+}/Co^{2+}$ that has a negative standard electrode potential,is $B.M.$ (Nearest integer).

The correct option with the order of melting points of the pairs $(Mn, Fe)$, $(Tc, Ru)$ and $(Re, Os)$ is $:$

Which elements of the $3d$ series do not show variable valency?

Assertion: Cuprous ion $(Cu^{+})$ has unpaired electrons while cupric ion $(Cu^{2+})$ does not.
Reason: Cuprous ion $(Cu^{+})$ is colourless whereas cupric ion $(Cu^{2+})$ is blue in the aqueous solution.